Plunger operated alternate action electrical snap switch



1965 E. R. CARLSON ETAL 3,213,229

PLUNGER OPERATED ALTERNATE ACTION ELECTRICAL SNAP SWITCH Filed June 17,1963 INVENTORS.

United States Patent 3,213,229 PLUNGER OPERATED ALTERNATE ACTIONELECTRICAL SNAP SWITCH Ernest R. Carlson, Fail-field, and CzeslawMackiewicz,

Trumbull, Conn., assignors to Harvey Hubbell, Incorporated, Bridgeport,Conn., a corporation of Connecticut Filed June 17, 1963, Ser. No.288,276 11 Claims. (Cl. 200-68) This invention relates to an electricalswitch and, more particularly, to a pushbutton switch especially suitedfor alternating current applications.

It has been discovered in practice that the make are developed duringswitching of alternating current deteriorates switching contacts fasterthan does the break arc. A fast making speed has been found to minimizearc damage. Conversely, it has been discovered that a slow breakingspeed is preferable to a fast breaking speed in the prevention of arcdamage. The reasons behind these discoveries are not completelyunderstood; however, the reason for the making phenomenon appearsselfevident, viz., reduced time and space for formation and duration ofarcing, whereas the reason for the breaking phenomenon appears lessclear, but is believed to be that the arc will extinguish itself duringa slow break at a minimum separation. If the break occurs at a fasterspeed, however, the arc becomes larger before it is extinguished by thenormal reversal of the alternating current.

Another factor to be taken into consideration in switch development isthat, for many residential and commercial lighting applications, thepushbutton switch has become quite popular. This type switch has asingle pushbutton element which is depressed to both open and close thecircuit. In contrast to the older type toggle switches and doublepushbutton switches, switches of this type often lack the force requiredto break contacts which may have become partially welded during theprevious closing stroke.

Accordingly, it is the primary object of this invention to provide animproved pushbutton switch for AC. use. Other objects are to providesuch a switch wherein a positive mechanical force may be applied foropening the switch, and to provide such a switch having a relativelyslow break speed and a fast make speed. These objects and others areattained by the novel switch mechanism of this invention. The switch ofthis invention may be most readily understood by reference to thefollowing specification, the appended claims, and the figures of theattached drawing, wherein:

FIG. 1 is a plan view, partially broken away for clarity, of a switchconstructed in accordance with this invention;

FIG. 2 is an elevational view, also partially broken away, of the switchof FIG. 1;

FIGS. 3 and 4 are cross sectional views of the switch operatingmechanism illustrating the operation of the switch;

FIG. 5 is an isometric View of the operating mechanism of the switch ofFIGS. 14;

3,213 ,229 Patented Oct. 19, 1965 portions are combined to providerecesses enclosing the switch mechanism. The housing is enclosed by acover plate 12 which defines a central opening surrounding a push button14. Push button 14 is substantially rectangular in horizontal sectionand includes first and second flanges 14a and 14b which extend beneaththe cover plate 12 for retaining the push button 14 in position. Theelectrical switching contacts are located in a switch chamber formedmainly in housing portion 10b. Housing portion 10a serves as a cover forthe switch chamber and also provides an intermediate shelf 16 betweenthe housing portions. The flanges 14a, 14b of the push button are urgedupwardly against the cover plate 12 by means of coil springs 18, 20which are compressed between the flanges and the shelf 16.

Push button 14 is hollowed out to form an internal V-shaped slot 22which is bounded by vertical side walls 22a, 221). A pivot pin 24extends between the side walls 22a, 22b and pivotally supports the endof a T-shaped plunger 26. Plunger 26 is positioned with the cross arm ofthe T-extending downwardly into the housing of the switch. A centralcavity in the housing portion 10a includes a pair of angled shoulders,28a and 28b, on one side of the T and a similar pair of shoulders on theoppo site side (not shown). Each pair of angled shoulders is sopositioned as to contact one end of the cross bar of the T-shapedplunger 26, and thereby serve as stationary cams for centering theplunger as it moves upwardly on the release of the push button, as willbe described in more detail infra.

Extending upwardly from base portion 10b and positioned directly beneaththe pivot pin 24 are a pair of knife-edged support members 30a, 30b. Thesupport members 30a, 3012 are spaced apart sufiiciently to allow roomfor an actuating coil spring 32 to extend between them. Mounted forrotation on the support members 30a, 30b is a hell crank 34. The bellcrank 34 is partially bifurcated to allow sufficient room for clearancefrom coil spring 32. The construction of the bell crank 34 is mostclearly illustrated in FIG. 5 and will be seen to include V notches 36which are mounted on the knife-edged support members 30a, 30b. Theupwardly extending arm of the bell crank 34 terminates in a pair ofelongated V-shaped sockets 34a, 34b. The horizontally extending arm ofthe bell crank is actually divided into two parallel arms 38a,

38b. The extremities of arms 38a, 38b terminate in a transverselyextending actuating bar 40. The ends of actuating bar 40 are slotted, asis clearly shown in FIG. 5. Through these slots extend the ends of themovable switch contact arms 42, 44. The switch contact arms 42, 44 carrymovable switching contacts 46, 48 which are arranged to contact eitherthe upper fixed contacts 50 or the lower fixed contacts 54, 56. Theswitch contact arms illustrated in FIGS. 1-4 are bent from strip stockso as to.include downwardly curved legs, such as 42', riveted, as byrivet 58 of FIG. 2, to respective contact terminal plates 60. In theembodiment of FIGS. l-4, the switch contact arms are pivotable upward ordownward about their bent portions. It is to be understood, however,that the switch contact arms 40, 42 are not resilient in the sense ofbeing springy. The details of the terminal construction are not requiredfor an understanding of the mechanism of the invention. External wiringconnections are made in the usual manner by means of binding screws 62.

As has been previously explained, the actuating coil spring 32 extendsin a generally horizontal position between the support members 30a, 30band between the horizontal arms 38a, 38b of bell crank 34. One end ofthe coil spring is secured to the actuating bar 40, as, for example, bybeing hooked into the first eyelet 90. The

J spring is stretched so as to be under tension and its other end ishooked into a second eyelet 92 which may be formed from a loop of wireanchored securely within the housing 10.

The operation of the invention illustrated in FIGS. 1-5 is as follows:The push button 14 is depressed (FIG. 2), thereby lowering the T-shapedplunger '26 until the cross bar of the T engages the V-shaped socket 34aon bell crank 34. As the button is further depressed to the positionillustrated in FIG. 3, it will be noted that the vertical displacementof the push button 14 and plunger 26 has been converted to rotationalmovement of the bell crank 34. Bell crank 34 rotates in acounterclockwise direction, which raises the actuating bar 40 to theposition illustrated in FIG. 3. At this point in the operation cycle,the right hand end of the coil spring 32 has been raised to the pointwhere the center line of the spring passes through the axis of rotationof the bell crank 34. This is, accordingly, the dead center position. Atthe same time it will be noted that, because the slot in the actuatingbar 40' is wider than the thickness of the switch contact arms 42, 44the contact arms themselves have not yet been affected. As soon as thisdead center position is passed, however, the spring 32 takes over theoperation and rotates the bell crank 34 to its extreme counterclockwiseposition illustrated in FIG. 4. During this interval, the lower edges ofthe slots in actuating bar 40 contact the switch contact arms 42, 44 andraise them upward, breaking contact with the lower fixed contacts 54, 56and making contact With the upper fixed contacts 50. This position isillustrated in FIG. 4 and it will be noted that the V-shaped socket 34aof the bell crank 34 has moved completely away from the T-shaped plunger26, solely under the influence of the spring 32. Accordingly, regardlessof how slowly the push button 14 may be depressed, the speed with whichthe movable contact approaches the upper fixed contact is fast and fixedby the spring constants. Further, if tripping of the contact does notoccur from spring action, because of prior contact welding, additionalpres- .sure on the push button will directly cause such tripping as aresult of the direct contact of the lower edges of the slots in actuator40 with the contact arms 42, 44 to break the weld. Further still, due tothe wide slots, a damping etfect is created which reduces contact bounceon make, as well as causing overtravel which generates increased contactpressure.

At the end of the switching cycle, as illustrated in FIG. 4, it will benoted that the plunger 26 is displaced from the vertical. Upon therelease of push button 14, the button is urged upwardly by springs 18,to its original position. As the button rises, one end of the cross barof the T-shaped plunger 26 contacts the angled shoulder 28a and theother end contacts the similar shoulder (not shown) on the other side ofthe plunger. These serve to cam the plunger 26 back to a centralposition. It will now be apparent that, with push button 14 raised andthe plunger 26 centered, the cross bar of the plunger T will be directlyabove the V-shaped socket 34b. Accordingly, a second depression of thepush button 14 will cause the bell crank to be rotated in a clockwisedirection and will thereby return the switch to its original state.Spring 32 powers the clockwise rotation of the mechanism in the samefashion as the counterclockwise rotation, causing contacts 46, 48 toclose rapidly against contacts 54,

66, they are provided with tongues which are recessed into correspondinggrooves 82 in the terminal blocks. In order to retain the knife edgeswithin their corresponding grooves, a positive axial force must beapplied to the contact arms. Accordingly, the actuating bar 84 of thisembodiment does not include the widely slotted ends of the actuating bar40. Rather, the actuating bar 84 is closely fitted to the cont-act arms64, 66 and abuts against a shoulder 64', 66' provided on each of thearms. Spring pressure from the coil spring 32 is then sufiicient toretain the contact arms in the grooves.

In the FIGS. 6, 7 and 8 modification, the switching mechanism trips freeas soon as the push button has been depressed sulficiently to causemovement of the end of the coil spring past its dead center position.Prior to such tripping, the movable switch contacts are directly liftedoff the fixed contacts by the actuator 84. This is a relatively slowbreak, which is desirable, and a direct forceful one which will breakany contact weld. However, once the dead center position is reached, thecoil spring takes over the operation and pulls the movable contact armsrapidly into the make position regardless of the speed of movement ofthe push button. It is also important to note that the initial break isactuated by direct mechanical pressure against the push button. Theadvantage of this is that any slight welding which may have occurredbetween the closed contacts can be broken by exerting additionalpressure on the push button. Accordingly, the switch of this inventionwill often be operable under circumstances wherein spring operatedswitches, for example, will remain welded closed.

While the preferred forms of this invention have been shown here, itwill be obvious to those skilled in the art that many other variationsand modifications may be made in its construction without departing fromthe spirit and scope of the invention as defined in the appended claims.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. An electrical switch which comprises: a housing; a cover on saidhousing having an opening therein; push button means positioned withinsaid opening and resiliently retained therein for movement into and outof said housing; elongated plunger means pivotally mounted by a firstend on said push button means and having a second end extending intosaid housing; bell crank means pivotally retained within said housingfor rotation between a first and a second position and including a firstand a second arm, the first arm of said bell crank means beingpositioned for engagement by said plunger means upon depression of saidpush button means to rotate said bell crank means between said first andsecond positions; switch contact means movable between a first and asecond switch position; actuating bar means atfixed to the second arm ofsaid bell crank means for movement therewith and substantially parallelto the axis of rotation of said bell crank means and arranged to actuatesaid switch contact means between said first and second switchpositions; and spring means operable against said actuating bar means tourge said switch contact means into the other of said switchingpositions.

2. The device of claim 1 wherein the first arm of said bell crank meansdefines thereon first and second sockets positioned to alternativelyreceive the second end of said plunger means when in said first andsecond positions.

3. The device of claim 1 wherein said spring means comprising a tensioncoil spring having a first end secured to said actuating bar means formovement therewith and a second end secured to said housing, the centerline of said spring passing through the axis of rotation of said bellcrank means during rotation of said bell crank means between said firstand second positions.

4. An electrical switch which comprises: a housing; a cover on saidhousing defining an opening therein; push button means resilientlyretained within said opening for movement into and out of said housing;elongated plunger means pivotally mounted by a first end on said pushbutton means and having a second end extending into said housing; bellcrank means pivotally retained within said housing for rotation betweena first and a second position and including a first and a second arm,the first arm of said bell crank means being positioned for engagementby said plunger means upon depression of said push button means torotate said bell crank means between said first and second positions;first and second switch contact arms movable between first and secondswitch positions; actuating bar means atfixed to the second arm of saidbell crank means for movement therewith and substantially parallel tothe axis of rotation of said bell crank means, said actuating bar meansarranged to displace both of said switch contact arms from either ofsaid first and second switch positions; and spring means operableagainst said actuating bar means to urge said switch contact arms intothe other of said switch positions.

5. The device of claim 4 wherein said actuating bar means com-prises afirst slotted end and a second slotted end, each of said switch contactarms passing through the slotted portion of a diiferent one of saidslotted ends.

6. The device of claim 5 wherein the width of the slot in each slottedend is greater than the thickness of the corresponding switch contactarm passing therethrough.

7. The device of claim 4 wherein said spring means comprises a tensionedcoil spring having a first end secured to said actuating bar means formovement therewith and a second end secured to said housing, the centerline of said spring passing through the axis of rotation of said bellcrank means during rotation of said bell crank means between said firstand second positions.

8. The device of claim 4 wherein said plunger means is substantiallyT-shaped and includes a cross arm at its second end; and wherein saidhousing includes stationary cam means positioned to engage said crossarm to urge said plunger means into a central position upon movement ofsaid push button means out of said housing.

9. The device of claim 8 wherein the first arm of said bell crank meansdefines a first and a second groove thereon, positioned to bealternatively engaged by said plunger means upon inward movement of saidpush button means to selectively rotate said bell crank means betweensaid first and second positions.

10. The device of claim 4 wherein each of said switch contact arms issubstantially L-shaped and flexes about its bent portion into said firstand second switch positions.

11. The device of claim 4 wherein each of said switch contact armsincludes a pivot end having a knife edge thereon and wherein saidhousing comprises a first terminal block defining a V-groove thereinreceiving the knife edge of said first contact arm, and a secondterminal block defining a V-groove therein receiving the knife edge ofsaid second contact arm.

References Cited by the Examiner UNITED STATES PATENTS 2,684,418 7/54Koch 200-453 3,051,810 8/62 Wahlstrom 200-153 FOREIGN PATENTS 896,1305/62 Great Britain.

BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner.

1. AN ELECTRICAL SWITCH WHICH COMPRISES: A HOUSING; A COVER ON SAIDHOUSING HAVING AN OPENING THEREIN; PUSH BUTTON MEANS POSITIONED WITHINSAID OPENING AND RESILIENTLY RETAINED THEREIN FOR MOVEMENT INTO AND OUTOF SAID HOUSING; ELONGATED PLUNGER MEANS PIVOTALLY MOUNTE BY A FIRST ENDON EACH PUSH BUTTON MEANS AND HAVING A SECOND END EXTENDING INTO SAIDHOUSING; BELL CRANK MEANS PIVOTALLY RETAINED WITHIN SAID HOUSING FORROTATION BETWEEN A FIRST AND A SECOND POSITION AND INCLUDING A FIRST ANDA SECOND ARM, THE FIRST ARM OF SAID BELL CRANK MEANS BEING POSITIONEDFOR ENGAGEMENT BY SAID PLUNGER MEANS UPON DEPRESSION OF SAID PUSH BUTTONMEANS TO ROTATE SAID BELL CRANK MEANS BETWEEN SAID FIRST AND SECONDPOSITIONS; SWITCH CONTACT MEANS MOVABLE BETWEEN A FIRST AND A SECONDSWITCH POSITION; ACTUATING BAR MEANS AFFIXED TO THE SECOND ARM OF SAIDBELL CRANK MEANS FOR MOVEMENT THEREWITH AND SUBSTANTIALLY PARALLEL TOTHE AXIS OF ROTATION OF SAID BELL CRANK MEANS AND ARRANGED TO ACTUATESAID SWITCH CONTACT MEANS BETWEEN SAID FIRST AND SECOND SWITCHPOSITIONS; AND SPRING MEANS OPERABLE AGAINST SAID ACTUATING BAR MEANS TOURGE SAID SWITCH CONTACT MEANS INTO THE OTHER OF SAID SWITCHINGPOSITIONS.